Items of this type based on composite materials are by way of example hose-shaped structures, in particular hoses and air spring bellows, drive belts, conveyor belts, and flexible containers. Among this group of items, particular mention may be made of hoses, where these consist of an internal layer and external layer and of embedded single- or multiple-ply reinforcement, and also optionally of further layers, for example of a diffusion-barrier layer. In this connection, reference is made in particular to the following patent literature: DE 42 32 946 C2, DE 10 2004 051 073 A1, DE 10 2008 014 988 A1, EP 0 567 115 B1, U.S. Pat. No. 6,009,911, EP 0 895 015 B1, EP 1 396 670 E1, EP 1 941 150 B1 and United States patent application publication 2009/0236004 A1.
In practical applications, items of the generic type use various types of reinforcement that reliably withstand the respective demands in relation to pressure and/or temperature and/or dynamic stresses and/or solvents, over the necessary service life. Materials that may be mentioned in relation to textile reinforcement are by way of example polyamides, aramids, and polyesters. The reinforcement bonded into the polymer matrix, for example into an as yet unvulcanized rubber mixture, for producing items based on elastomers or thermoplastic elastomers, or into a molten plastic, for producing thermoplastic items, is achieved in a very wide variety of forms, for example in the form of fibers, yarns, cords, and filaments, or else in the form of sheet-like structures which in turn by way of example can be knitted fabrics, non-wovens, woven fabrics, and braided fabrics. Finally, the reinforcement is bonded into the material by way of the vulcanization process or another hardening process.
The hoses in particular are utilized in a wide range of applications involving different requirements, and the decision to use any particular reinforcement here is always taken after assessment of suitability and costs.
Particularly stringent requirements are placed upon hoses used in the air-intake region of supercharged internal combustion engines (EP 1 396 670 B1), and therefore on the reinforcement in these hoses. Further details of the prior art relevant here are given hereinafter.
Supercharged engines are constantly increasing in popularity in the market because this technology can achieve significant improvement not only in fuel economy but also in exhaust-gas quality in accordance with EU Standard. The technical principle can be described in its simplest form as follows: the air needed for the combustion process is compressed by way of a supercharger in order to increase the absolute content of oxygen, which makes up only about 21% of atmospheric air. The compressed air is then cooled by way of a charge-air cooler and then forced into the combustion chamber. The mounting of the charge-air cooler is located on the vehicle body, separate from the engine, and the charge-air hoses that connect the charge-air cooler to the system therefore have to withstand high pressure and thermal stresses. Under running conditions, furthermore the substantial relative movements of engine and vehicle body also subject them to permanent dynamic stress due to a wide variety of spatial deflections in all possible directions. Processes that occur in the actual charge-air system are not only compression and transport of air but also deposition of fuel residues and lubricant admixtures within the piping, and the polymer material has to withstand these over the service life of an automobile.
In principle, the materials to be used can be varied as required by the usage conditions, but specifically for reinforcement hitherto only a restricted selection has been available, for high temperatures in conjunction with high pressure. Applications of this type generally use yarns/twisted yarns based on meta-aramid.